1. Field of the Invention
The present invention relates to a compact electronic equipment having a statistical function. More particularly, the present invention relates to a compact electronic calculator having a function for calculating a process capability index.
2. Description of the Related Art
Some compact electronic equipment having a statistical function have a function for displaying a statistical graph. However, such electronic equipment can not display a graph of a mean value or a standard deviation of the displayed statistical data. Therefore, it is impossible to see any trend of a distribution of the data.
In particular, a compact electronic calculator can not make a calculation which requires statistical processing such as a calculation of a process capability index that is used as an index for quality control. Therefore, for example, to obtain a process capability index, it is necessary to obtain statistics (a mean value and a standard deviation) of the statistical data and to manually calculate the process capability index based on a specification range defined by upper and lower specification limits decided by a user. As a result, the calculation is troublesome when the statistical data are added and/or deleted.
Japanese Laid-Open Patent Publication No. 2-302622 discloses an analysis display system of a histogram, in which digital values of a maximum value, a minimum value and a mean value of histogram data between two optional points on the histogram and a linear histogram of the mean value are displayed over the histogram. Also in the electronic calculator of this system, however, a process capability index and the like should be manually calculated every time the statistical data are varied.